This invention relates generally to an electrical conductor cable having multiple conductor wires for carrying a plurality of different electrical signals. More particularly, this invention relates to an improved lightweight and pliable flat conductor cable designed for long-term use substantially without degradation or failure due to exposure to ultraviolet radiation or temperature extremes.
Electrical conductor cables, sometimes referred as wiring harnesses, typically include a plurality of elongated conductor elements for carrying a plurality of electrical signals, for example, between components of electronic equipment as in a computer system or the like. The conductor elements commonly comprise elongated wires of a conductive material, such as copper or the like, having a generally round cross-sectional shape and individually jacketed by an appropriate insulation material. The plurality of insulated wires are assembled into generally parallel relation and collectively retained within an outer wrap of insulation material to form the conductor cable. In accordance with one common cable geometry, the conductor wires are bundle together to form a cable having a generally round cross-sectional shape with sufficient flexibility and compactness for use in a wide range of applications. However, in some cable installation applications, particularly such as a spacecraft environment, substantially increased cable flexibility and reduced cable thickness can be highly desirable to accommodate volumetric size constraints. In such applications, the conductor wires are assembled into a generally coplanar or flat cable configuration. Moreover, in a spacecraft environment, the insulation material encasing the conductor wires preferably comprises a specialized material which will maintain the desired level of flexibility and dielectric properties during use in outer space.
In the past, one dielectric material found to be especially suited for use in an outer space environment without significant degradation comprises a polyimide sheet material manufactured and sold by E. I. du Pont de Nemours and Company, Wilmington, Delaware, under the trademark Kapton. More specifically, Kapton polyimide sheet material is a lightweight and highly pliable substance possessing excellent dielectric properties and adequate tensile strength for use as an insulation material for electrical conductor elements. Moreover, Kapton sheet material is highly resistant to physical degradation in an outer space environment including, for example, resistance to embrittlement from exposure to ultraviolet radiation or from outgassing in a vacuum and resistance to degradation from exposure to temperature extremes within a range typically encountered in outer space. However, Kapton sheet material resists conventional thermal forming and shaping processes and thus heretofore has not been formed into a configuration satisfactory for use as a flat cable insulation material.
More particularly, flat conductor cables have been constructed to include a plurality of round wire conductors insulated individually by spirally wrapped strips of Kapton sheet material, with the thus-wrapped conductors being retained in a flat cable configuration within an outer jacket typically of a molded polyester plastic or the like. However, the outer jacket is subject to degradation in an outer space environment thereby providing significant potential for cable failure over a period of time. Moreover, the use of spirally wrapped Kapton strips particularly in addition to the outer jacket of a different material undesirably and unacceptably increases the overall thickness and stiffness of the flat conductor cable.
Alternative flat conductor cables have been developed using Kapton sheet material for insulating thin ribbon-like conductor elements in lieu of conventional round wire conductors, as described above. In such alternative cables, a plurality of the ribbon-like conductor elements are retained in spaced, generally parallel relation between two plies of Kapton sheet material bonded together with an appropriate adhesive. While such cables possess a substantially minimum thickness and further have exhibited a high degree of longevity in outer space use, each of the plurality of thin conductor elements must have a substantial width to provide the necessary current-carrying capacity. As a result, the overall width of the flat conductor cable becomes unduly large and unacceptable for many installation applications.
There exists, therefore, a significant need for an improved flat conductor cable of the type having a plurality of round wire conductors, wherein the round wire conductors are encased by formed plies of Kapton sheet material for optimum flexibility, compactness, and longevity in an outer space environment. The present invention fulfills these needs an provides further related advantages.